But analysts say it's not time to panic just yet. The money that flowed out of the markets over the past three years is just starting to make its way back in.

"Looking at thebigger picture, there is a lot of room for this rally to continue, and any pullbacks will be small and contained," said Ryan Detrick, senior technical strategist at Schaeffer's Investment Research.

The S&P 500 is still about 20% off its October 2007 all-time high of 1,565.

It's not all champagne and roses. Some say this bull run is largely due to the Federal Reserve's easy monetary policy, and once the central bank decides to unwind its support, the market will unravel.

"As long as the Fed keeps printing money, stocks will go higher on that momentum," said Joseph Saluzzi, co-head of equity trading at Themis Trading. "But there is going to be a point when the momentum will break. We don't know when it will happen, but it will be ugly."

On Thursday, stocks rebounded from afternoon lows and finished with small losses as oil prices retreated from two-year highs above $100 a barrel. The Dow Jones industrial average (INDU) finished 37 points lower, or 0.3%, and the S&P 500 (SPX) slipped 1 point, or 0.1%.

The recent spike in crude prices above $100 a barrel has investors "on the defensive," said Scott Marcoullier, chief technical market strategist at Wells Fargo Advisors. The market's weakness follows two days of steep losses.

Meanwhile, the Nasdaq (COMP) managed to gain 15 points, or 0.6%, thanks in part to a 9% jump in shares of Priceline.com (PCLN). The online travel-booking service reported a 73% jump in fourth quarter profit after the market close on Wednesday.

Companies:Shares of Sears Holdings (SHLD, Fortune 500) dropped 6% after the company reported a 13% drop in profit and as sales declined at its namesake retail stores. The stock was among the biggest decliners on the S&P 500 and the Nasdaq. Sears also named Lou D'Ambrosio as CEO and president, succeeding Bruce Johnson, who had been interim CEO for three years.

There's a long list of companies that Donald Trump has publicly attacked. But you know what they say about there being no such thing as bad publicity? Shares of companies Trump has criticized are beating the market since the election. More